Method and mold for molding hollow rubber articles



Sept. 13, 1932.

METHOD AND MOLD FOR MOLDING HOLLOW RUBBER ARTICLES Filed Jan. 15, 1930 JTZaW 1 Wan/4 PatentedY Sept. 13, 1932 UNITED STATES lPAT-ENT oFFIcE JAMES ALLAN LAW, OF k.ASCO'JL VALE, VICTORIA, AUSTRALIA MnTHoDANn Morin non MonnINe HOLLOW RUBBER ARTICLES l Application filed January 15, 1930, Serial No. 421,013, and in Australia March 6, 1929.

An object of my invention is to produce improved hollow balls suitable for use in playing tennis; and a further object isA to enable manufacture to be effected at a'low cost. I avoid the production and subsequent combination .of rubber elements each constituting half a hollow ball, because such re,- sults in an internal ridgewhich destroys uniformity. I also avoid processes which cause the balls to be uneven in the thickness of the rubber.

By my process and apparatus a ball is made which is free from uneveness and which, awing to its uniformity, will rebound truly and be very durable.

I take rubber material of suitable quality,- in the trade called compound, but hereafter, for brevity, simply termed rubber, and mold Y it into ball shape on a supported spherical core inside a mold having a spherical cavity, and I partly cure the ball thus made. It then has a hole due to the space occupied by the core support and when I employva distance piece between the mold top inner surcaused by it. I remove the partly made ball from the core and if theball interior should be lined or coated, in any well known manner, with material which will prevent escape of compressed air or gas subsequently admitted, I apply the said lining or coating. Any VeX- ternal web which may occur in making my ball would be thin and would be removed easily by known methods.

I treat the hole edges, and collapse the ball, leaving the hole exposed, and apply a hole filled of the same or virtually the same material as that of the ball. There may be at this stage a relatively small hole in the ballY and when air enters through it the ball recovers its normal shape; but if the hole is absent I make one. f 2 f I provide a plug by which later on to seal the said hole, but before said sealing I grip the ball in a circular apertureof a register plate, the aperture diameter being slightly smaller than the ball diameter. close the ball in a spherical chamber in which the ball fits closely.

The register pate 1s removed to allow the I then en- Y ThroughV the chamber hole I eXtend a plunger for depressinga plug to make the latter close the ball hole. Before actuating said means I place the chamber in a chest to which air or gas under pressure is admitted, ,l

and upon the ball becoming charged I de- Y press the means by which the plug is sealed. The ballis deformed by the plunger depression but this is only vtemporaryas when the hole is sealed the plunger'is raised. The Y ball is then ready for completion of. thecuring, which is effected. My ball is free from all internal projections, is of uniform thickness, and has no joint or seam which, if present, would preventk all parts of the ball lhaving uniform resilience anddurability. Y

The ball could be cured prior to the filling withcompressed air or gas, in which case,

to press and fiX in place any hole filling e. Y To understand the foregoing and other features of the invention, reference should be made to the accompanying drawing which illustrates suitable apparatus for carrying my process into effect, except that in practice a plurality of balls would be made simultaneously, and it is .not necessary to here illustrate means of mass production.

The construction shownV can be varied while retaining any matter hereinafter claimed.

EXceptingFigures 10 and 11 allv these views are .central sections. As suitable piece, an electrically heated member is usaface and the core there will be a small hole b1 Y forms of press are knownfin the trade I do not illustrate any. Y

Figure' 1 is a perspective view showing mold and adjacent partsincludinga core.

Figure?, is an elevationof a mold lower part, acore, some'unmolded rubber, and some molded rubber. v

Figure 3 shows the parts in Figure 2, and withl the core enclosed by rubber which is enclosed inthe mold.

,Figurefi showsfan alternative mold containing a core, and rubber positioned for pressure into the molding space.

Figure showsI the rubber covered core after the rubber has been partly cured and the mold opened, and said core raised from the mold lower element.

Figure 6 shows the rubber covered core mounted on a handle and held near a hook which is applicable to stretch the hole in the ball and enable removal of the ball from the core.

Figure 7 shows the removed ball, and means to prepare the edge of its hole to receive a hole iilling piece.

Figure 8 shows the ball collapsed, with a hole filling piece, and a plunger to press said piece down evenly in correct position so that itfills and closes the hole permanently.

Figure 9 shows the ball with a relatively small hole provided in it to allow ofv the introduction of compressed air or gas.

Figure 10 is a perspective view of' part of a registering plate.

Figure 11 shows-on a larger scale-a sealing pin. Y

Figure 12 shows a two part box or chamf ber, its base carrying said registering plate and the ball of Figure 9,-,the pin of Figure'11, and a plug to seal the relatively. small air hole, beingL also shown.

Figure 13 shows the parts in Figure 12, with the box closed, the registering plate having been removed, andthe box containing the, balls enclosed in a casing. The plug fixing pin is shown in two of its positions. The` stage shown is that at which compressed air or gas has been supplied in the casing whereby the balls have become filled.

Figurey 14 shows a. fragment of a known ball having an internal circumferential rib and joint, but inv practice frequently the joint is more imperfect by reason of a circular crack existing which leaves the rubber thinT n er. Y

` Figure 15 shows a fragment of another known ball which is defective because of the irregular thickness of its rubber.

Figure 16 showsmuch enlarged--a distance piece as used in some cases to ensure corel centralization.

Figure 17 shows-also enlarged-fa,y frag.

vtop elements of a mold, each having an the core having peg admission means, repre-V Y sented by a hole 1a. An air way 1s provided in ,thel peg as shown at 3b to let air escape from the mold. The shortest distance from the core to the mold equals the thickness of the rubber of the ball to be made, subject to f any-slight effect of the further treatment.

Mold elements 1a, 1* advantageously in practice adjoin press elements 6a, 6P, having steam chambers 7a, "b, commonly used in this art.

The mold to contain the rubber, which, being plastic yields to pressure, especially when heatec is heated, and rubber 8 is placed in element 1a, see Figure 1, and the spherical core L.lf-of metal usually-is depressed on the rubber, the molding surfaces being concentric, the rubber spreading as at 8a, any siilrplus rubber projecting around the mold e ge. v

Additional rubber 9 is placed on the core, s ee Figure 2,-and the mold top is depressed on it to spread it as at 9, making it meet land Vbecome homogeneous with theY lower rubber, and ill the molding space. Any surplus rubber present extrudes intoa spew way or channel 10 and can be discarded.

. The alternative mold in Figure 4 is apertured to receive rubber 9b, and it is convenient to employ inthe aperture a tube 11, in which a plunger 12 is worked to cause the plastic uncured rubber'to advance and fill the spherical 'molding space, subject to the prest ence of a'peg4 3, surplus rubber extruding through passages 10a into spew way 10A The moldingfsurface 123 of plunger 12 if; concave and registers with the mold.

' Therubber-coatingfonthe core, produced in any way described, is then, in trade language., lightly semi-cured'. This partial curing permits of the removal 0fthe ball from the core. The mold is opened andthe coated core is removedsuitable means being shown in Figure where 131is a pusherintroduced through the peg; its pressur'eon the core interior lifts the core relatively to the pcg and to the mold lower part. In Figure G a holder 14.` is shown entered in h ole A@to allow the core and ball f to be held conveniently while'the latter separated from the core.- Anyv suitable separating means maybe employed; I' find that a hook 15 if engaged with ball hole 16 enlarges ity suiiiciently.,

The edge of hole 16 is trued by any obviousmeans; thus17 is a grinding tool, and the edges are evened so that they contact closely and unite strongly with a filling piece 18, tobe fixedV by suitable known meansfor in which it fits.

example adhesive. To allow of applying the piece 18, the ball 9c is collapsed and supported on, for example, the convex block 19.

I prefer to press the filling piece edges unn der those of a tubular holder 20, within which is a plunger 21. Although a heavy metal core will ordinarily when used as described become accurately located for molding, yet I add in some cases a positive locator comprising a distance piece 1C, Figure 16, )rejecting from the mold part 1b into a core recess 1lb, the effect being in addition that the ball will have a small hole 22", Figure 17 This hole is useful as hereinafter described. It allows of the admission of air to let the ball resume its spherical shape. If when piece 13 closes the ball there is no hole 22", I make a small hole 22, air entering which acts as stated.

In Cases in which a hole 22 is to be made, I provide, to indicate the spot 22b1 at which to make it, a nipple 22a in mold 1b, or on plunger 12.

The ball is charged with compressed air or gas before hole 22 is sealed; then the ball is cured and covered with fabric, if required for playing tennis. Referring to Figures 1() to 13, 23 is a thin register plate having circular holes 24 such that a ball, placed in one of them, is gripped or slightly compressed, it being well to set the ball with its air hole uppermost. This plate is shown in sections 23, 23b connected at 23. I locate the ball lower half in the lower part 25 of a chamber I also provide a plug 26, which has a conical point usually, ready to close the said hole the edges of which may be coated with adhesive.

The chamber upper part 27 is then set in place and the register plate removed, so that the chamber is closed. This chamber has a` hole 28 registering with ball hole 22. A sealing pin or plunger 29 is fitted in hole 28. It is shown grooved at 2)a for air passage. This pin has plug 26 below it.

The chamber is by suitable means, such as bolts 30 carrying each a nut 30a, held closed, and is itself enclosed in a chest 31 which is made air-tight, and is charged with air or gas under pressure, 32 being a supply duct and 33 a gauge. When the balls are charged, pin 29 is depressed by for example the pressure of a member 34. This causes a local deformation of the ball shape shown at 29h, but that deformation disappears when the pressure is relieved.

I lock pin 29, with the plug of the sealed ball B Figure 13, held in position. Thus a catch 37 engages a pin notch 36.

The chest is opened, and the chamber is removed, and curing completed, after which the chamber is opened and the balls taken out.

In the claims which follow the word ball means a hollow resilient ball; and the word rubber7 means rubber material or compound cavities therein Vto ideinela chamber, aY peg y passable through one section and extending into the chamber, a spherical core having a socket therein removably engaging the peg and serving to maintain the core spaced from air escape passage. therein, and an ejector extending through the air passage for dislodging the core from the peg. Y

2. A mold for the purpose specified consisting of complementary sections having cavities therein to dene a spherical chamber, a peg carried by one section and extending medially into the chamber, a spherical core having a socket therein receiving the peg, means for permitting air from the chamber to escape through the peg, and means passable through the peg for dislodging the core therefrom.

3. A mold for the purpose specified comprising complementary separable sections having cavities therein defining a chamber, a peg carried by one section and extending into the chamber, the other section having an aperture therein, a core removably engaged on the peg and maintained through the medium of the peg spaced from the wall of the chamber, and a plunger for forcing the material to be molded through the aperture into the chamber.

4. A Vmethod of forming hollow rubber balls which consists in forming minute holes in the balls, placing the balls in chambers, then placing the chambers ina chest, supplying the chest with fluid under pressure to enter the balls through the holes, and using pins for forcing closure plugs into the holes.

5. A mold for forminghollow rubber articles comprising Vcomplementary sections having concavities therein defining a chamber, a core in the chamber, means extended into the chamber for engaging the core, a distance piece carried by one section and engaged with the core and cooperating with said means to hold the core centralized in the chamber.

6. A mold as claimed in claim 5 wherein the distance piece forms a hole in the article the wall of the chamber, said peg having anv ,80

moldythen drawin'gth'e' 'core through the main hole,.then plugging the main hole and forcing air under pressure into the ball through the minute hole, `and then completing the curing of the ball.

In Witness whereof I have hereunto signed my name. to this specification at Melbourne in the State of Victoria, in Australia, this g eighteenth day of December, 1929.

Cil

,JAMES ALLAN LAW. 

